Worm gearing



Dec. 9 B LAZ ICH ET AL WORM GEARING Original Filed Jan. 14, 1 930 4 Sheets-Sheet 1 E amlmm INKENTORS Brcmlso Lazzch and By Harry E. Ash wpmh.

THEIR ATTORNEY Dec. 8, 1936. B. LAZICH ET AL WORM GEARING Original Filed Jan. 14, 1930 4 Sheets-Sheet 2 INKENTORS Branlzo Lazzch and y HQPII/ CZ/KL THE/H A TTORN Dec. 1936. B. LAZICH ET A1. mwm

WORM GEARING Original Filed Jan. 14, 1930 4 Sheets-Sheet 3 INYENTORS Br'anho LazLch and y Harry E. ska/01 th THEIR ATTORNEY Dec. 8, 1936. B. LAZICH ET AL WORM GEARING Original Filed Jan; 14, 1930 4 Sheets-Sheet 4 INVENTORS EiAshwmPh QR W THE/H ATTORNEY Bpanlzo Lazwlz and I0 IIIH Patented Dec. 8, 1936 UNITED STATES PATENT OFFICE WORM GEARING Original application January 14, 1930,. Serial No. 420,736. Divided and this application June 28,

1934, Serial No. 732,856

2 Claims. (01. 74425) Our invention relates to electrical relays, and particularly to relays oi the type comprising a winding and a contact which is operated at the expirationof a time interval of predetermined length and of comparatively long duration after said windingbecomes energized.

One object oiour invention is to provide a relay of the type described in which the length of the time interval which elapses between the energization of its winding and the operation of its contact may be adjusted to any desired value.

Another object of our invention is to provide a'relay of the type described which is so constructed as to provide maximum reliability of operation.

The present application is a division of our copending application, Serial No. 420,736, filed onJanuary 14, 1930 for Electrical relays.

We will describe one form of relay embodying ourinvention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig.1 is a view, showing in side elevation, one form of relay embodying our invention, with certain of the parts omitted to illustrate the construction.

Fig. 2 is a front view of the relay illustrated.

in Fig. 1. Fig. 3 is a rear View of the relay illustrated in Figs. 1 and 2. Fig. 4 is a top plan view of the neutral armature for the relay illustrated in Figs. 1, 2 and 3. Fig. 5 is a view showing, on a somewhat larger scale, the contactv arm F for the relay illustrated in Figs. 1, 2 and 3, as it appears when viewed from the left in Fig. 3. Fig. 6 is a top plan view, drawn to the same scale as Fig. 5, of the contact arm for the relay. illustrated'in Figs. 1, 2 and 3. Fig. 7 is a fragmental view showing in isometric projection the magnetic clutch and drive shaft 26 forming a part of the. relay illustratedin Figs. 1, 2 and 3. Fig. 8 is a detail view showing the pawl and ratchet mechanismfor rotating. the drive shaft 26.. in response to oscillation of the auxiliary armature 21, as it appears when viewed from the right in Fig. 1. Fig. 9 is a diagrammatic view showing. one circuit arrangement which may be used with the relay shown in Figs. 1, 2 and 3..

Similar reference characters) refer to similar parts in each of the several views.

Referring first to Figs. 1, 2 and.3, the relay comprises a top plate A. of suitable insulating material, such as porcelain or hard rubber, which serves as a support for all of the operating parts of the relay. Mounted on the top plate A are three magnetizable cores I, 2 and 3, the upper ends of which are connected together bya back strap 4, and the lower ends of which terminate, on the under side of the top plate A, in enlarged polepieces l 2*, and 3**, respectively. The core I is provided with a coil tend the core 2 is through the downwardly extending lugs of a nonmagnetizable bracket I l which is fastened to the sides of the pole pieces I and 2 by means of screws I 2, asbest seen in Fig. 1. The opposite.

ends of the armature 9 are provided with extenssions 9 and-9 (see Fig. 4) which extensions 00-". operate with two auxiliary electromagnetsB and C, respectively. These electromagnets are similar and, in the form here shown, and best illustrated in Figs. 1 and 2, each comprises a magnetizable core 2| extending downwardly from a magnetizable arm 22, and provided with a winding 23 and an elongated pole piece 24. The arm 22 of the electromagnet B is attached to the side of the pole piece 2 by means of screws 25, andthe arm--22 of electromagnetC' is similarly attached" The parts of to the sideof the pole piece l the electromagnets B and C are so arranged that when neutral armature 9 is swung away from the pole pieces Wand 2 to its lower position in which it is illustrated in the drawings, the upper side of the pole piece 24 of electromagnet B will be parallel to, and will engage the underside of the extension 9 of armature 9, and the upperside of pole piece 24 of electromagnet C will be parallel to, and will engage the underside of the extension 9 of armature 9. The function of the electromagnets B and C will be explained in detail hereinafter.

A plurality of contact fingers, hereshown as four in number, and designated l3, l4, l5, and

[6, are attached to the under side of the armature 9 by means of insulating supports ll. When armature 9 is swung away from the pole pieces I and 2?, as shown in the drawings, the contact fingers l3, l4, and I5 each engage a back con-" tact i8 to close contacts l3-|8, I4--l8, and

l5l8=, whilethe contact finger I6 engages a back contact 19 to close a contact l6-l9. When armature 9 is swung towards the pole pieces I and 2 however, the contacts [3-48, I l-l8, i5l8, and 16-19 are all opened, and the contact finger l5 then engages a front contact 15 l5'15, while the contactto close a contact finger l6 engages a front contact 20 to close a contact Iii-29.

The front contact and the back contacts Hland I9 are attached to terminal posts 15 w and I9 respectively, mounted on the topplate A, as shown in Figs. 1 and 2, while .16 pieces I and 2 on two pivot pins l9. threaded".

the front contact 20 is attached to a similar terminal post which is not shown in the drawings, but which is also mounted on top plate A.

As best seen in Figs. 1, 7 and 8, pole piece 3* of core 3 is bifurcated, and pivotally supported at its centre on a drive shaft 26 journaled in the bifurcations of pole piece 3, is an auxiliary armature 21. The pole pieces I and 2 have integral extensions 28 and 29, respectively, the pole faces of which overlie the armature 21 at its opposite ends. The armature 21 is arranged to swing toward one or the other of these pole faces, non-magnetizable stops 3!] (Fig. 8) being attached to the armature to prevent the armature from coming into actual contact with the pole faces.

The auxiliary armature 21 is provided at one end with a contact finger 3! (Fig. 3) which is attached to the underside of the armature by means of an insulating support 32 and, at the other end, with a similar contact finger 33 which is similarly attached to the armature by means of an insulating support 34. When the armature 21 is swung toward the pole face of extension 28 of pole piece l as shown in the drawings, the contact finger 33 engages a fixed contact 35 fastened to a terminal post 35 mounted on the top plate A, to close a normal contact 3335, and the contact finger 3i engages a fixed contact 36attached to a terminal post 36, also mounted on the top plate A, to close a normal contact 3|--36. When armature 21 is swung toward the pole face of extension 29 of pole piece 2 however, the contact finger 33 then engages a fixed contact 3'! to close a reverse contact 3331, and the contact finger 3| engages a fixed contact 38 to close a reverse contact 3l38. The fixed contact 31 is attached to a terminal post 3'! mounted on the top plate A, and the fixed contact 38 is attached to a similar terminal post also mounted on top plate A, but not shown in the drawings. While we have shown only two contact fingers attached to the armature 21 for simplicity in illustrating our invention, it is understood that additional contact fingers may be attached to this armature when desired.

As will be explained more fully hereinafter, the auxiliary armature 21 may at times be made to oscillate. When this armature is oscillating, the motion of the armature in one direction is transmitted to the drive shaft 26 by means of a pawl and ratchet mechanism (Figs. 1, 3, and 8), the pawl 39 being carried by a stud 4D projecting from the side of the armature 21, and the ratchet wheel 4| being secured to one end of the drive shaft 26. The pawl 39 is normally held in engagement with the ratchet wheel M by gravity. Rotation of the drive shaft 26 in the direction opposite from that imparted to the drive shaft by the pawl and ratchet mechanism is prevented by a dog 42 of suitable resilient material secured to the underside of the extension 28 of the pole piece 1*, and arranged to successively engage the teeth of the ratchet wheel 4! as the wheel is rotated by the dog.

Mounted on the opposite end of the drive shaft 26 from the ratchet wheel 4! is a contact arm designated in general by the reference character F. As here shown, the contact arm F comprises two parallel plates 46 and 4'! secured together by spacing studs 48, as best seen in Figs. 1 and 5. The plate 46 is provided with two integral spaced lugs 46 and 46 and secured to a short shaft 56 which is journaled in these lugs is a worm 51. The worm 5'! meshes with a worm wheel 58, the hub 59 of which extends through, and is journaled in, a hole l! in the plate 41. Attached to the outer end of the hub 59 is a segment 63 which holds the worm wheel in place. The upper end 56 of the shaft 56 is made rectangular in shape to enable the shaft to be turned by a wrench or other suitable tool, and it will be apparent that when this shaft is turned, the worm 51 rotates the worm wheel 53, thereby changing the position of the seg ment 60 with respect to the plates 46 and 41. The segment 60 is provided with a scale, as best seen in Fig. 1, and the plate 41 has formed on its lower end a pointer 4'17 which moves along this scale as the position of the segment with respect to the plates 46 and 4'! is varied. The reason for varying the relative position of the segment GB and the plates 46 and 4! will be ex plained in detail hereinafter.

When the segment 60 has been adjusted to a predetermined position with respect to the plates 45 and 41, it is desirable to hold the segment in this position and, for this purpose, we provide a locking member, here shown as a strip 6! of flexible material, such as phosphor bronze. One end of the strip 6| is fastened to the lug 43* by means of screws 62, and the other end of the strip is bent upwardly, and is provided with a rectangular slot 6| which is just wide enough to receive the upper end 56 of the short shaft 56 when the sides of the rectangular end 56 are parallel to the sides of the slot 6|. With the parts of the arm F locked in this manner, when it is desired to change the position of the segment 6i! with respect to the plates 41 and 48, the inclined end of the strip 6| is depressed as by the tool which is utilized for turning the shaft 55 until this end is below the rectangular end 56 of the shaft 56, whereupon the shaft 53 may be rotated until the segment 68 occupies the desired position. It will be apparent that as soon as the tool is removed from the shaft, the free end of the strip 6| will automatically return to its inclined locking position provided the shaft occupies a position in which the sides of the end 56 are parallel to the sides of the slot 61 The drive shaft 26 extends through the hub 59 of the worm wheel 58 and through a hole 46 in the plate 46 with sufficient clearance to permit the contact arm F to rotate about the drive shaft, and has attached to its outer end a pinion 43 which holds the contact arm F on the drive shaft. The pinion 43 meshes with a gear wheel 44 secured to one end of a countershaft 45. The countershaft 45 is journaled in suitable holes in the plates 46 and 41 of the arm F, and carries on its other end a pinion 33 which meshes with a gear wheel 50 mounted on a bushing loosely journaled on the drive shaft The gear wheel 50 is attached to, or formed integral with, a clutch wheel which, as here shown, is a knurled metal wheel, but which may, if desired, be constructed of any other suitable material, such for example, as cork, leather, or a condensation product of phenol. The clutch wheel 5| is at times engaged by a knurled stud 52 forming a part of a magnetic clutch which we will now describe.

This magnetic clutch, as best seen in Fig. 7, comprises a magnetizable member 53, pivotally supported on a pin 54 carried by a projection on one of the bifurcations of the pole piece 3 and arranged to be attracted toward the pole piece 3 and the extensions: 28and; 291' of: the

pole pieces I and 2"; respectively, wheneither: or'both. of the coils5, and G areenergized. The knurled stud 52 is attached. to the lower end of the member 53 by' means ofa short strip 52 preferably of flexible material; and-the parts areso arranged that when theimagnetizable mem= ber 53f-is attracted towards the :pole piece3 and the extensions 28 and 29, the stud 52 will engage the clutch wheel. 5| and prevent rotation of the gear wheel 56. Two counterweights 55, attached to. the. upper part of the magnetizable member 53, bias this member to a position in which the stud 52 is out of engagement with/the clutch wheel 5|.

The contact arm F is biasednby gravityto. a positionin which an insulating strip 63 attached to the lug 46 engages a stop 13 fastened to a terminal post 65 mounted onithe top plate A as best seen in Fig. 3. Whenthe arm; occupies this position, the strip 63: also engages a. contact finger 64' and: moves it into engagement.

with a contact finger. 65 to close a contactD.

The contact finger 65 is attached :to the terminal. post 65*, while the contact finger .64 is attached to a similar terminal post (it also mounted on the top. plate A. Suitable stops 66' are attached to the terminal posts 65* and 64 to limit the spacing: between the contact fingers when the strip 63 is moved out of engagement with the contact finger 64. i

The contact arm F also controls a contact E comprising two spaced contact fingers l0 and .H attached by meansof studs 68 to'a blocktl' of insulating material, which block,: in; turn, is

fastened by means ofa bracket fifito a terminal post 69 mounted on the top plate A. The-contact finger 10 is provided with top'and bottom stops l0 and. 10 and the contact finger H is provided with abottom stop H l The contact E isarranged to be closed,; in a manner which Will be described in detail hereinafter, by an insulating. piece 12 riveted to a lug (m formed on-the segment 60 of the contact arm F.

Referring now to the wiring diagram for therelay shown in Fig. 9; the two windings of, the coil.5 referred to hereinbefore are designated. by

the reference characters 5' and 5 ,,respectively,-

and the two windings" of the coil 6 are designated by the reference characters 6 and 6 Current is suppliedto. these windingsand to the winding 23 of each of the auxiliary electromagnets B and C from a suitable source, such as a battery G, over a. circuit controller H which may be operated in any suitable manner.

As shown in the drawings, circuit controller H is open so that windings5 and 5 of coil. 5,

windings S and 6' of. coil 6, andwindings 23 of the electromagnets B andC. are all. derenergized. The neutral'armature 9 is therefore swung away from pole pieces l and 2* so that contacts l3-l8, Ml8, I5-l8,. and Iii-I9 are: closed, while contacts l5-T5 and I6'20 are open. Auxiliary armature 2! is swung toward extension 28 of pole piece l and normal contacts over .contact I 5-4 8, but only winding 16 becomes,

energized because windings; 5 and. 6 are; short? circuited. over a circuit whichtincludes contact l3-IB,, and winding '5 is short-circuited-over a circuit-which includes contacts I 3-! 6,11 4--I 8, -As-a result;.auxiliary armature 2'! is swung toward" extension 29 of polepiece 2 andthe magnetizabiemember 53 of the mag-.- netic clutch is. attracted to the pole piece 3 andithe*extensionsliland 29 of the pole pieces and: 2 The neutral. armature 9, however,-; is held away fromzthe pole :pieces I and 72 under these.conditions-because the windings 23 of the auxiliary electromagnets B and" C are de-energized; and the reluctance. of the; path to the neutral. armature throughnthe magnetic structures; of the auxiliaryelectromagnets-B and C for'theflux: set upby the winding: 6 is lower than: the. reluctance: of the path tothe neutral armature through the air gaps between the pole pieces. I and 2 and the: neutral armature, and.- more flux-therefore reaches the neutral armature throughzthe'magnetic structured the auxiliary electromagnets than through the air gaps between thepole pieces I and! and theneutral armature; It follows that'the tractive' force exerted to'liftth'exarmature 9 toward pole pieces I and 2 is less than the combined force of gravityand the effect of the flux through the magnetic structures of electromagnetsB and C. Theicontacts I3-l8, l4'-'--l8, l5--I8' and I6--l9' controlled by the neutral armature therefore remain closed even though winding Ee of coil 6 is now energized.

When the auxiliary armature 21 is swungto-- wards extention 29 ofpole piece 2*, the normal contacts fill-36 and 33'-35 controlled by this armature are? opened, andthe reverse contacts 3l-3B and 33 -31 become; closed. Since contacts l4l6 and l5-'-|8. are'still closed, the closing of reverse contacts 3I-38 short circuits to? winding 6 of coil 6,'and the field set up by this winding commences to decay. Due, however, to theisnubbing effect of the circuit for winding 6 and; to the sleeve 1" andi. washers 8 on thecore 3, thisdecayis comparatively slow. The openin'grofthe contact 3 l-36- meantime has allowed winding 5 to becomeenergized. The-growtlrof' the flux: set:-up by this latter winding:- is comparatively slow; however, due" to the sleeve land. washers: 8 on core 3 but, after an interval of time, the torque exerted on armature 21 by this flux over-balances the torque exerted on arma-e ture 21 by. the decaying flux inwinding 6 and armature 21 thenswings back. toward extension 26wof pole piece I. This motion first opens reverse-contacts 3l--38 and 33-3! and their closes normal contacts'3l-36 and 33-35. The neutral. armature 9 is still held away from the pole pieces I and 2 during this movement of the armature 21 for the reasons: pointed out here'- inbefore, so-that contacts l3I8,ll4-l8, l5*-IB, and still closed; and winding 5 therefore again becomesenergizediand winding 5 again becomes shorti-circuited. The field: of' winding 6 then slowly" builds up and .the field of winding 5* slowly decays, this: decay beingretarded by. the self inductance of winding 5*; and by sleeve 3, and :the washers 6. that auxiliary'armature 21' is positively swung to and fro aslong as circuit controllen H is closed and. the winding. 23 of the auxiliary electromagnets B and 0 remain 'de-energized, and itwillalso be clear that a considerable interval of time 'elapses between" armaturemovements;

It willv therefore be clear" Iii-l9 controlled by: the armature 9 are It should be pointed out that this time interval is substantially independent of fluctuations of the electromotive force in the energy supply because the auxiliary armature is acted upon by two opposing forces both of which increase or decrease as the electromotive force of the energy supply increases or decreases. This time interval, however, may be varied by varying the rate at which the flux in this core builds up or decays, t is variation being effected, with the apparatus constructed in the manner here shown, by varying the number of washers 8 on core 3.

Each time auxiliary armature 21 is swung towards pole piece 29, drive shaft 26 is rotated through a small are due to the pawl and ratchet mechanism described hereinbefore. This rotation of the drive shaft 26 is transmitted through the pinion 43 to the gear wheel 44 which, in turn, drives pinion 49. Since the magnetizable member 53 is now swung towards pole piece 3 and the extensions 28 and 29 of the pole pieces H and 2*, gear wheel 50 is prevented from rotating by the engagement of knurled stud 52 with the clutch wheel and it will be apparent, therefore, that the pinion 43, gear wheel 44, pinion 49, and gear wheel 50 constitute a planetary drive by means of which contact arm F is rotated around the drive shaft 26 as a pivot, the direction of such rotation being clockwise as seen in Fig. 3. As soon as the contact arm has been rotated through a small arc; the resultant movement of the insulated strip 63 permits contact finger 64 to move out of engagement with contact finger 65, thereby opening contact D; and, when the arm has been rotated through a sufficiently large arc, the insulating piece 12 attached to segment 60 engages contact finger II and moves it into engagement with contact finger 10, thereby closing contact E.

When contact E becomes closed, current from battery G is supplied to the windings 23 of the electromagnets B and C in series if contact 3|--36 is closed, or if this contact is not closed, then on the next operation of armature 21 which closes this contact, the circuit for these windings including, in addition to contact E and contact 3|-36, contact |4-| 8 and circuit controller H, as will be apparent from an inspection of Fig. 9. The windings 23 are connected in this circuit in such manner that the fluxes created in the cores 2| of the auxiliary electromagnets B and C by the current in these windings thread the cores 2| in the opposite direction from the flux which threads these cores due to current in either of the windings 5 and 6 and the parts are so proportioned that the magnitude of the flux in the cores 2| due to the current in the windings 23 is sufliciently great that the flux which threads the armature 9 through the air gaps be-' tween the armature 9 and the pole pieces I a and 2 under these conditions will exert a torque on the armature which causes the armature to swing toward the pole pieces I and 2 Shortly after the armature 9 starts to swing toward the pole pieces I and 2*, contacts |4--|8, |5|8, and l6--l 9 are opened, but contact |3|B is adjusted to remain closed until the armature has moved a short distance beyond the point in its upward travel at which the contacts |4-|8, |5|8, and |E3--|9 open. When contacts |4|8 and |5|8 are opened, winding 6 which is normally energized when these contacts are closed and contact 3|-36 is closed, becomes de-energized and, at the same time, the short circuit which is normally completed for winding 5 at contact |4|8 when contact 31-36 is closed, is opened. Winding 5 is then supplied with current in series with the windings 23 of the electromagnets B and C over contact |3|8 which, as pointed out hereinbefore, remains closed after contacts |4|8 and |5|8 are opened, and winding 5 therefore becomes energized and supplies fiux to the armature 9 in place of winding 6 The resistance of the windings 23 will usually be considerably less than the resistance of the winding 5, so that the magnitude of the flux which is supplied to armature 9 due to the current in winding 5 under these conditions will be only slightly less than the magnitude of the flux which was supplied to the armature 9 due to current in winding 6 and it will be apparent, therefore, that the opening of contacts |4|8 and |5|8 has very little effect on the torque exerted on the armature tending to move the armature toward the pole pieces I and 2*. As soon as winding 6* becomes tie-energized and winding 5 becomes energized in the manner just described, auxiliary armature 21 stops oscillating and this armature is then held in the position in which its normal contacts 3|36 and 3335 are closed. When contact |3-|8 opens, the short circuit which was previously closed for windings 5 and 6 at this contact, is opened, and the windings 5 5 6 and 23 in series are then all supplied with current from battery G over contact E and circuit controller H, so that these windings are all energized. The windings 5 and 6 are preferably constructed to have a comparatively high resistance in order to limit to a low value the current supplied to the relay from battery G after these windings become energized. When armature 9 has completed its upward stroke contacts |5-'|5 and |B20 become closed. As long as circuit controller H now remains closed the windings 5 5 6 and 23 will continue to be energized because the magnetic clutch is held in the position in which the stud 52 engages the clutch wheel 5|, so that the contact arm F is held in the position in which contact E is closed. It will be apparent, therefore, that after the neutral armature has once been attracted: to the pole pieces I and 2 this armature will be held in the position which it then occupies until circuit controller H is opened to ole-energize the relay. When this is done, the neutral armature 9 drops away from the pole pieces I and 2 thereby opening contacts |5--'|5 and lB-ZO, and closing contacts |3-|8, MI8, |5| 8 and Iii-I9. Furthermore, the magnetic clutch drops away from the pole piece 3 and the extensions 28 and 29 of the pole pieces I and 2*, respectively, thereby permitting the contact arm to return by gravity to its normal position. When the contact arm returns to its normal position, contact E is opened and contact D becomes closed. When contact D becomes closed, the parts of the relay are then restored to their normal positions in which they are illustrated in the drawings.

It will be noted in Fig. 9 that when armature 9 is picked up, winding 6 is short-circuited by contact |515. As a result, when the relay becomes de-energized, the self-inductance of winding fi retards the decay of flux which threads the neutral armature, and hence causes the neutral armature to be slow-releasing. Under some conditions it may be desirable to cause the neutral armature to release more quickly upon the de-energization of the relay and, when this is the case, this contact may be omitted.

The time interval which elapses between the energization of the relay and the closing of contact E depends upon the rate at which armature 21 oscillates, upon the gear ratios of the planetary drive for the contact arm F, and upon the length of the arc through which the contact arm F must rotate from its normal position before insulating piece 12 closes contact E. The rate at which armature 21 oscillates may be varied by varying the proportioning of the parts, and by varying the number of washers 8 on core 3, as pointed out hereinbefore; the gear ratios of the planetary drive may be varied by replacing the gear wheels with other gear wheels having the desired ratio, as will be readily understood; and the length of the are through which the contact arm F has to move from its normal position in order to close contact E may be varied by varying the relative position of the segment 60 with respect to the plates 46 and 41 in the manner which has also been previously described. It will be apparent, therefore, that the time interval which elapses betwen the energization of the relay and the closing of contact E may be adjusted to any desired value.

For any given gear ratio and proportioning of the parts the time interval required for the operation of the relay may be indicated by the position of the pointer 41 on the scale which is provided on segment 60 by suitably calibrating this scale so that the graduations on this scale correspond to the correct time intervals,

It is desirable that adjustments in the length of the time interval which elapses between the energization of the relay and the closing of contact E due to changes in the position of the segment 60 with respect to the plates 46 and 47 of the contact arm F may be made from the top of the relay, and, for this purpose, we provide a bushing '72 which is mounted in the top plate A in such manner that the bushing is directly above the vertical shaft 56 when the contact arm occupies its normal position, as shown in Fig. 3. The upper end of this bushing is threaded to receive a nut 12 by means of which the top of the bushing may be closed. With the parts constructed in this manner, when it is desired to change the position of the segment 6!! with respect to the plates 46 and 41 of the arm F, the nut '12 is removed from the top of the bushing, and the shaft 56 is turned by a suitable tool inserted through the bushing 12.

The contact D serves as a check to indicate that the contact arm F has returned to its normal position when the relay becomes de-energized. This contact may be used to control any suitable form of indicating apparatus in any suitable manner.

The normal contact 3335 and reverse contact 33--31 controlled by the auxiliary armature 21, and the contacts I6-l9 and I6-20 controlled by the neutral armature may be utilized to control any desired circuits in any suitable manner forming no part of our present invention and therefore not shown in the drawings.

From the foregoing, it will be apparent that we have provided a time element relay in which a definite time interval of adjustable length and of comparatively long duration may be made to elapse between the energization of the relay and the closing of contact E.

One advantage of a relay embodying our invention is that, since the contacts l3--l8, l4-l8 and |5--I8 are included in the circuits over which current is supplied to the windings of the relay before contact E becomes closed, the neutral armature is positively prevented from picking up until this contact becomes closed. For, if, due, for example, to vibration or to some fault in the magnetic structure of the auxiliary electromagnets B and C, or to excessive voltage supplied to either or both of the windings 5 and 6 the neutral armature starts to move toward the pole pieces I and 2 before contact E becomes closed, then, as soon as the motion of the armature starts, the contacts I l-l8 and 15-48 open and deenergized, so winding 5 or 6 which is then energized, so that the armature 9 immediately returns to its lower position.

Another advantage of a relay embodying our invention is that due to the construction and arrangement of the parts a high degree of accuracy in the time required for the operation of contact E is obtained.

Still another advantage of a relay embodying our invention is that the relay is constructed with a minimum of parts arranged to provide maximum reliability of operation.

Although we have herein shown and described only one form of relay embodying our invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of our invention.

Having thus described our invention, what we claim is:

l. A contact arm comprising a plate, a worm Wheel having a hub rotatable in said plate, a segment secured to said hub on the opposite side of said plate from said Worm wheel and arranged to hold said worm wheel in place, a rotatable shaft secured to said plate and provided at its upper end with a rectangular head to receive a tool for turning the shaft, a worm attached to said shaft and meshing with said worm wheel for rotating said worm wheel in response to rotation of said shaft, and a locking member for said shaft comprising a flexible strip having one end inclined and provided with a rectangular slot which is just wide enough to receive the rectangular head of said shaft when the sides of said rectangular end are parallel with said slot, said strip being attached to said plate in such manner that its inclined end must be depressed past said head before said shaft can be rotated.

2. In a contact arm, the combination of two parallel plates secured together by spacing studs, two lugs integral with one of said plates, a shaft journaled in said lugs and adapted to receive a tool for turning said shaft, a worm secured to said shaft, a worm wheel meshing with said worm and having a hub journaled in one of said plates, a segment attached to said hub on the opposite side of said one plate from said worm wheel and arranged to hold said worm wheel in place, a scale on said segment, a pointer on said one plate arranged to cooperate with the scale on said segment, and locking means for normally preventing rotation of said shaft.

BRANKO LAZICH. HARRY E. ASHWOR'I'H. 

